CS Rotterdam

As a part of the extension of the local public transport between the cities of Rotterdam, Den Haag and Zoetermeer, the subway station Rotterdam Centraal will be newly organised and reconstructed. For this, a water-tight excavation pit must be created around the station mainly by means of a surrounding diaphragm wall which is approximately 38 m embeddedin the ground. The civil works will take place on the station’s forecourt during running subway and tram operation. In the penetration area of the existing tunnel section into the excavation pit, the creating of the watertight excavation pit is only possible, by means of freezing the ground due to barriers in the building ground. Groundwater flows up to 4 m/day in Pleistocene sand require a seldom used combination of nitrogen and brine freezing process.
By simultaneously using liquid nitrogen and brine, a closed frozen body was created within two months. During the time for freezing up, the hourly throughput of liquid nitrogen was up to 8.000 kg. A laborious tube system supplied the 51 nitrogen and 52 brine freeze pipes with the two refrigerants. That way, an arch-shaped frozen body which is approximately 50 m in length, 38 m in depth and up to 5 m thick was created. For maintenance over a period of nine month, only the cascade refrigeration plant with a refrigerating capacity of 275 kW is operated. During this time, the nitrogen system serves as a back-up system. A comprehensive temperature monitoring with 500 individual temperature sensors monitors and records all building states in and in the direct environment of the ice wall.
The scope of the building works which will last from December 2006 to October 2008 include:
  • the drilling works for the freeze pipes within the metro tunnel
  • installation and removal of he the brine and nitrogen tubes with flow pipe and return pipe
  • installation and control of the freezing plant with pump station
  • installation and removal as well as control of the digital systems for measurement and control, approximately 650 measurement and control channels are installed
  • care of the freezing system during the entire construction time



    Frankfurter Ring 105
    D-80807 Munich, Germany
    Phone + 49 89 350607-11327
    Fax + 49 89 350607-25
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